Conversion of calcium compounds



great difliculties in practice.

" tles out quickly and the Patented Jan. -27, 1931 T D ST TE PATEN os 'ca i oT ro BA Z mm WILHELM WAGNER, or LunwxssHarEN-oN-rnn nmnn GERMANY, ASSIGNORS TO I. a; nannnmnnus'rarn AKrrnnGnsEnLscHAFnor FRANKFORT-ON- THETMAIN, GERMANY, a CORPORATION OF'GER-MANY' r Y l 1 coiwnnsion or cemoiu i oolvrrounns J No Drawing. 'App1ication filed m a, 1923, ser ai nof aaaaesf a amm Jul 11,1927.

Gypsum, when obtained by double dematerial containing calcium compounds often separates in a more or less mucilagino'us form, which is unfavorable, for its separa tion from the mother liquor and presents We have now foundthat the settling of the gypsum and its separation is much facili-- tated if the decomposition is carriedout in the presenceof metaphosphoric acid which expression is meant to comprise also its salts insofar asthese are soluble in the reaction liquid. The gypsum is thus obtained granular and uniform in character, so that it setfiltration proceeds smoothlyand rapidly.

When converting for instance potassium sulphate and calcium nitrate into potassium nitrate and calcium sulphate, or when decomposing phosphate rock with sulfuricacid or acid salts of sulfuric acid to obtain free phos phoric acid or acid salts of same, say for example acid potassium phosphate, small sential advantage, that the extensive foam-V amounts of meta-phosphoric acid are added to the reaction mixture, thus causing the gypsum to separate in an easily filterable form. The said addition further provides theess ing occurring during the'decomposition of [many phosphates with sulfuric acid is con- 'siderably lessened.

phoric acid'to be added varies'with the dif-- ,ferent initial materials treated and can easily i The amountof the said compounds necessary to be added to efiect granular crysta'llization of gypsum is small. Generally speak- 'ing, only a few per cent up to about 10 percent of metaphosphoric acid calculated on the amount of calcium compound treatedare suificient for producing the desired result though even less than one per centfor instance about 0.3 per cent may be employed occasionally. The exact amount of metaphosbeidetermined by a few tests. Moreover it is not necessary to add a fresh amount-of metaphosphoric acid to every new charge as at least part of the requisite amount can be supplied by reintroducingpart of the mother liquor resulting from a previous treatment "of the mother liquor freed from-the calcium sulphate deposited, and' containing a considerable amountfof the said addition, for instancewhen decomposing phosphate rock. This reintroduced'part of aprevious treatment serves also asa diluentfor the sulfuric acid necessary for decomposing" the fresh charge.

the 3 added metaphosphoric Tliusniotqonly p 7 is utilized to a large extent, butthe said manner of working enables in a simple manner phosphoric 'acid of a'high concentra tron, VlZ. about l0 Brand more'to be obtained,.since sulfuric acid; of much higher concentration can be. employed for effecting Y decomposition, without running the risk-of a 'nearly'inseparable pasty mixture of gypsum with'phosphoric and sulfuric acidbeing formed."

. The following examples will'further illus} trate the nature of the said invention Whichhoweverjis not limited thereto:

tassium sulphate beingthen addedto the hot solution; ,l/Vhenthe conversion is completed thegranular gypsumcan beea'sily filtered oiif 7 from the potassium nitrate solution; p

v,5,tons of vMoroccophosphate are converted witl ta. dilute'sulfuric acid containing 3.21tons.

of sulfur; trioxid, i11 which about 30 to 6 0 to lkilo-gram ofmetaphosphoric' V i BJsolutiOh of calcium nitrate, about 320 kil-; I

"kilograms of sodium metaphosphateare disx solved After-the reaction has proceeded for e er l, h urs h dep it d gyps m w h is of agranular character, j can be. eas ly 1 0 tons of a per cent Y pebble phosphate 1 Whichinithe ordinarywayof decomposition with sulfuric acidyieldsa gypsun'i'of thick" pasty consistency: settling' only )With diffi- V culty, -are treated with dilute sulfuric acid,

containing about 633-;t0ns of jsulfur-trioxid. '7

lQQliil-egr ms f c lailim metaph spha igaazze.

The gypsum obtained settles readily and can be easily filtered off from the phosphoric acid solutions. V

p Example 4 V r I '1 ton of Morocco phosphate is treated with an aqueous solution containing 25 kilograms of sulfuric acid, 680 kilograms e of: sodium bisulfate' and to 10 kilograms of: free metaphosphoric acid; After the reaction has proceeded for several hours, thegypsum,

which has settled down as agranular pre-f c cipitate, can be easilyfiltered 05 from the solution" of acid sodium phosphate. If pebble phosphate be employed instead of Morocco phosphate, an adidtion of only from 2 to 5 kilograms of metaphosphoric acid will be sufiicient. V

Eaiaa mple i5 7 I I ton of Morocco phosphate is introduced into 2 cubic meters of a mixture of a 23 B.

I phosphoric ac dand sulfuric acid containing 620 kilograms of sulfur trioxid in which with a sulfuric acid the step of reintroducing .part of. the mother liquor from a previous charge containing metaphosphoric acid into the process and adding such small amounts of, metaphosph'oric acid: that the reaction mixture contains between about 0.3 and 10 per cent thereof-calculated on: V

the amount of calcium, compounds present,

In testimony whereof we have hereunto set our hands. F v OTTO BALZ.

WILHELM WAGNER. i

the following charge, instead of the above said 2 to 3 cubic meters of a 39? B. phosphoric acid.-- In this case; therefore ,no' or at i t leastmuch less of freshmetaphosphoric acid 'is' to'be added to obtain the described effect,

than to thefirst charge V v -;Wl1at we claimis; g f 1. In thedecomposition of materials con-.

' taining a' calcium compound With a comstep of adding small amounts-0f metaphos- V pound containing ajsulfuric acid radical the phoric acid.

2. In the decomposition of m'at'erials contaming a calcium :compound with seem:

pound containing a sulfuric acid radical the;

step of'addi'ng between aboutfi0.3;and' 10 per cent calculated; on'the amount of-calciugi compound employed of'metaphosphoric .2101 I, r j I i .3. In the decompositionof phosphate rock v with a compound containinga sulfuric acid 7 radical the step of. addingsmall amounts of metaphosphoric acid.

l. In the decomposition of phosphate rock 7 V with sulfuric acid the step'c of'adding between about 0.8 andlO per cent of metaphos phoric acid calculated on the amount 7 of phesphat rock employed. v V L'5.In the decoinposition 'ofpliosphate'rockg f-iE- 

